0001-Don-t-call-QueryVariableInfo-on-EFI-1.10-machines.patch

From 493bd940e5c6e28e673034687de7adef9529efff Mon Sep 17 00:00:00 2001
From: Peter Jones <pjones@redhat.com>
Date: Sat, 10 Apr 2021 16:05:23 -0400
Subject: [PATCH] Don't call QueryVariableInfo() on EFI 1.10 machines

The EFI 1.10 spec (and presumably earlier revisions as well) didn't have
RT->QueryVariableInfo(), and on Chris Murphy's MacBookPro8,2 , that
memory appears to be initialized randomly.

This patch changes it to not call RT->QueryVariableInfo() if the
EFI_RUNTIME_SERVICES table's major revision is less than two, and
assumes our maximum variable size is 1024 in that case.

Signed-off-by: Peter Jones <pjones@redhat.com>
---
 mok.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/mok.c b/mok.c
index 9b8fc2b..beac0ff 100644
--- a/mok.c
+++ b/mok.c
@@ -261,6 +261,9 @@ static const uint8_t null_sha256[32] = { 0, };
 
 typedef UINTN SIZE_T;
 
+#define EFI_MAJOR_VERSION(tablep) ((UINT16)((((tablep)->Hdr.Revision) >> 16) & 0xfffful))
+#define EFI_MINOR_VERSION(tablep) ((UINT16)(((tablep)->Hdr.Revision) & 0xfffful))
+
 static EFI_STATUS
 get_max_var_sz(UINT32 attrs, SIZE_T *max_var_szp)
 {
@@ -270,11 +273,21 @@ get_max_var_sz(UINT32 attrs, SIZE_T *max_var_szp)
 	uint64_t max_var_sz = 0;
 
 	*max_var_szp = 0;
-	efi_status = gRT->QueryVariableInfo(attrs, &max_storage_sz,
-					    &remaining_sz, &max_var_sz);
-	if (EFI_ERROR(efi_status)) {
-		perror(L"Could not get variable storage info: %r\n", efi_status);
-		return efi_status;
+	if (EFI_MAJOR_VERSION(gRT) < 2) {
+		dprint(L"EFI %d.%d; no RT->QueryVariableInfo().  Using 1024!\n",
+		       EFI_MAJOR_VERSION(gRT), EFI_MINOR_VERSION(gRT));
+		max_var_sz = remaining_sz = max_storage_sz = 1024;
+		efi_status = EFI_SUCCESS;
+	} else {
+		dprint(L"calling RT->QueryVariableInfo() at 0x%lx\n",
+		       gRT->QueryVariableInfo);
+		efi_status = gRT->QueryVariableInfo(attrs, &max_storage_sz,
+						    &remaining_sz, &max_var_sz);
+		if (EFI_ERROR(efi_status)) {
+			perror(L"Could not get variable storage info: %r\n",
+			       efi_status);
+			return efi_status;
+		}
 	}
 
 	/*
-- 
2.33.0.309.g3052b89438-goog